Anti-pollution screen for agricultural dryer and method of removing pollutants

ABSTRACT

A simple and inexpensive anti-pollution screen and the method of using it for dryers of particulate matter are disclosed which in its preferred form make use of existing dryer frame members for supporting the screen and take advantage of the heat produced by the drying operation to prevent sticking of the unwanted particles to the screen. The normal vibration produced in the frame by the fan and burner associated with the dryer shakes down any unwanted particles lodged in the screen. Readily releasable means are provided for removing a portion or all of the screen to gain access to the accumulated unwanted particles at the bottom of the dryer.

United States Patent 1191 Alms [ ANTI-POLLUTION SCREEN FOR AGRICULTURAL DRYER AND METHOD OF REMOVING POLLUTANTS [76] Inventor: Erhard E. Alms, 419 Valentia Ave.,

Barrington, 111. 60010 [22] Filed: Dec. 1, 1971 [21] Appl. No.: 203,791

3,057,080 10/1962 Haddix 34/174 July 24, 1973 Primary Examiner-John J. Camby Attorney-Charles F. Voytech [57] ABSTRACT A simple and inexpensive anti-pollution screen and the method of using it for dryers of particulate matter are disclosed which in its preferred form make use of existing dryer frame members for supporting the screen and take advantage of the heat produced by the drying operation to prevent sticking of the unwanted particles to the screen. The normal vibration produced in the frame by the fan and burner associated with the dryer shakes down any unwanted particles lodged in the screen. Readily releasable means are provided for removing a portion or all of the screen to gain access to the accumulated unwanted particles at the bottom of the dryer.

12 Claims, 6 Drawing Figures PAYTENTEDJULZMBH SHEET 2 [IF 2 ANTI-POLLUTION SCREEN FOR AGRICULTURAL DRYER AND METHOD OF REMOVING POLLUTANTS This invention relates to dryers for particulate matter such as grain and particularly to a method and means for preventing the discharge of foreign matter mixed with the grain into the surrounding atmosphere.

Grain dryers such as the one disclosed in Arthur Andersen U.S. Pat. No. 3,056,214, dated Oct. 2, 1962, are used at elevators, feed mills and on larger farms to remove excess moisture from grain to be stored. Such dryers are provided with perforated substantially vertically disposed double walls defining between them a columnar space into which grain to be dried is fed from a bin. Two such double-walled columns are provided, the walls being curved to meet at the top and bottom of the dryer where the feed and discharge augers are located. In the space between the curved columns of grain is located the burner and plenum and chamber which supply the heated air for the drying process, aided by one or more powerful fans which, together with the expansion caused by rapidly heating the air, create a pressure differential in the columns decreasing toward the outside of the columns. The ends of the dryer are closed with unperforated metal sheets. The pressure differential across the columns of grain causes foreign particles in the grain to be blown out into the surrounding atmosphere and carried for some distance from the dryer by the wind. Such wind-carried particles are objectionable air pollutants.

It has been proposed to eliminate the wind-carried particles by enclosing the dryer in a screened shed in which the particles would be trapped. This involves additional expense for the screen structure and it has also been found to be unsatisfactory, particularly with continuous dryers, as compared with batch-type dryers. The foreign particles pass through the perforated walls of the dryer into air that has become cool and they strike the cooled screen along with the moisture-laden air from the drying operation to form a wet mass that adheres to, and clogs, the screen. The clogged screen interferes with the free movement of drying air through the columns by reducing the pressure differential across the columns, and it necessitates frequent shutdowns of the dryer to clean the screen.

It is thus an object of this invention to provide means, on a dryer for grain, for removing foreign particles from the air leaving the dryer, which means is quite simple and inexpensive to install and maintain.

As a more specific object, this invention seeks to provide a means for removing foreign particles from the air leaving a grain dryer, which means does not require the building of a separate structure around the dryer.

A further object of this invention is to provide a means for removing foreign particles from the air leaving a grain dryer which means is non-clogging and hence is self-cleaning so that it requires no maintenance such as screen cleaning and reversing during a drying run.

It is also an object of this invention to provide a method of removing pollutants from air leaving a grain dryer which method takes advantage of the cooling cycle forming part of the grain drying cycle to prevent the pollutants from sticking to a screen used in the process as a filter.

These and other objects of this invention will become apparent from the following detailed description of a preferred embodiment of the invention when taken together with the accompanying drawings in which:

FIG. 1 is a perspective view of a grain dryer in which the screen of this invention has been installed;

FIG. 2 is an enlarged fragmentary section of the upper part of the screen and dryer taken along line 2-2 of FIG. 1; i

FIG. 3 is an enlarged fragmentary section of the lower part of the screen and dryer taken along line 3-3 of FIG. 1;

FIG. 4 is an enlarged fragmentary section of the intermediate part of the screen and dryer taken along line 4-4 of FIG. 1;

FIG. 5 is a longitudinal section through the dryer of FIG. 1; and

FIG. 6 is an enlarged fragmentary side elevational view of a holding means for the screen.

The several objectives of this invention given above are accomplished by taking advantage of the structure of an existing dryer to gain support for the screen of this invention, and by taking advantage of a function forming part of the method of operation of the said dryer to maintain the foreign particles in a dry state at all times, thus to prevent clogging of the screen. F urther, a condition of the dryer when it is in operation is utilized to loosen particles which may be lodged in the screen.

In the aforementioned existing dryer, the columnar bins of the dryer are made from a skeletal frame, comprising vertically disposed parallel ribs made of angle irons one side of each of which angle iron is disposed parallel with the longitudinal axis of the dryer to provide a surface to which perforated sheets can be bolted to form the smooth inner walls of the bin. The other side, or leg of the angle iron extends outward from the columnar bin at right angle to the axis of the dryer and may be from one to two inches wide.

In general, the foreign particles found in grain to be dried are comprised of fragmented grain, parts of the husks or corn cobs and other bits of plants found near the grain in the field. These particles are soft and flocculent in the case of husks and bits of plants, and granular in the case of fragmented grain. The perforations in the bin walls through which heated air from the innerplenum chamber passes are small enough to hold the grain, but are large enough to allow those foreign particles to pass through. The screen size for catching the particles after they leave the bin is regulated by State Pollution Control Boards and in one state is 24 mesh.

However, the moisture-laden air from the bins also passes through the perforations with the particles and if the particles are allowed to remain in that air when it cools to ambient temperature, the moisture therein condenses on the particles and they become soggy and soon clog the screen. It is therefore necessary to cool the particles with air that is substantially unheated and unmoistened by the grain and hence much drier than the heated air passing through the wet corn. In batchtype dryers, a cooling cycle for the grain is automatically programmed into the grain drying cycle to prevent condensation of moisture in the grain and the consequent nullifying of the drying cycle, and accordingly,

the present invention is particularly well adapted for use with dryers into which a drying cycle is programmed.

Although the cooling cycle is effected by operating the blowers of the dryer without burning any fuel, the

temperature of the air of the bin walls and of the angle iron skeletal dryer frame a short distance from the perforated bin walls is still relatively high, on the order of 140 150 F., due to the heat extracted from the heated grain by the unheated air. The temperature drop increases, however, with the distance from the bin wall, partly because of the expansion of the heated air as it leaves the bin and partly because of its mixing with the outside air. Thus, if the screen is located at that distance from the bin wall at which it is still hot, the air issuing from the dryer during the cooling cycle for the dried grain can be used to cool the particles without reintroducing moisture thereinto, and the particles will remain hot and dry either on the screen or in the space between the screen and bin wall where gravity will cause them to fall into a prepared clean-out area or receptacle.

The location of the screen relative to the perforated bin wall should thus be selected to maintain the particles in a dry state at all times, and to provide adequate space between the screen and perforated bin wall for the particles to fall through to the clean-out receptacle or area. 1 have found that from one to two inches is adequate spacing, and that such spacing may be provided by the ribs used as a frame for a dryer. Thus if the screen is placed upon and secured to the angle iron frame over the edges of the outwardly extending sides of angle irons, the screen will remain dry during the entire grain drying cycle and the particles will have ample room to fall away from the screen.

It is also desirable, even with dry foreign particles which exhibit no tendency to adhere to one another or to the screen, to provide a mechanical shaking action to the screen, particularly where, as in the dryer illustrated herein, the screen is not flat and vertical, to promote movement of the particles down the screen into a receptacle or clean-out area. In the dryer mentioned above, the vibration of the fans and their associated drives, and the vibration resulting from the periodic turning on and off of the burner for temperature control, create sufficient vibration in the frame and the ribs to which the screen is attached to eliminate the need for any additional mechanical shaker for the screen.

Referring now to the drawings for a detailed description of the invention illustrated therein, the dryer to which the invention can be applied may be of the type disclosed in the aforementioned Andersen US. Pat. No. 3,056,214, said dryer being shown in FIG, 4 and schematically in FIG. 5. Thus it may be comprised of spaced perforated sheet metal walls and 11 defining between them columnar bins for holding grain 12 to be dried. Two such pairs of walls are used to define two columnar bins which are curved to meet at the top and bottom where they are in communication with a load auger 13 at the top of the bins and an unload auger 14 located at the bottom of the bins. The columns are loaded periodically with wet grain and subsequently unloaded when the grain is dry. The ends of the walls are closed at one end by an imperforate sheet 15 and at the other end by a similar imperforate sheet 16 in which is formed a large opening 17 leading to the burner 18, for heating the air to be used for drying the grain. Upstream of burner 18 is a fan 19 driven by a motor 20 which drives ambient outside air into the burner section 21 and on into a plenum chamber 22. The heated air is then forced through the perforations 23 and 24 of the walls 10 and 11, respectively, and

through the grain disposed between said walls to extract by heat a predetermined portion of the moisture in said grain.

The walls 10 and 11 are held by a skeletal frame which is designated generally by the reference character 25 (FIG. 1) and which is constructed of angle irons suitably shaped and secured together to provide adequate support for the walls and also to provide support from an appropriate foundation for the dryer as a whole. Thus the dryer may be comprised of the curved walls 10 and 11 which are secured respectively to spaced angle iron ribs 26 located on the inside of the dryer and similar spaced angle iron ribs 27 located at corresponding places on the outside of the dryer, each angle iron rib having a side 28, 29 which is parallel to the plane of the perforated wall to be supported thereby and secured thereto by appropriate bolts or other fasteners (not shown) and a side 30, 31 which extends transversely of the axis of the dryer.

The outer ribs are connected at their lower regions to vertically disposed struts 32 and to a horizontal angle iron frame portion 33 constituting the base 25 for the dryer. Said base may in turn be supported on a concrete slab or as shown here upon a concrete block structure such as is shown at 34. It may be noted that base 25 is as long as the dryer but is narrower than the widest rounded portion of the dryer. It may be noted further that said base may serve as a receptacle for the unwanted solid particles leaving the outer perforated walls of the dryer from which said particles may be removed periodically.

As described in detail in the aforementioned Andersen patent, the dryer is provided with controls which automatically till the dryer, heat the grain in the dryer to drive off the moisture therein to a predetermined minimum moisture content and then coolthe grain to prevent the moisture in the air from condensing back on the grain and nullifying the drying operation. The air is heated by burner 18 and is blown by fan 19, operated by motor 20, into the plenum chamber 22 during the heating cycle. During the cooling cycle burner 18 is shut off and fan 19 is operated to bring in ambient air from outside the dryer, said ambient air passing into the plenum chamber 22 which has been heated by the previous heating cycle, through the hot perforated walls and grain to the exterior atmosphere. The ambient air thus leaves the dryer at a higher temperature than the outside air, it having extracted heat from the plenum chamber, dryer walls and the grain therein. Thus the air leaving the dryer during the cooling cycle may be initially at to F. and gradually drops to a temperature somewhat above ambient temperature and well above the dew point of the moisture in the air. This air from the cooling cycle is utilized in the screen and screening process to prevent the condensation of moisture upon the screen and in the particles adjacent thereto which if allowed to form would create a soggy mass which would adhere to the screen and gradually block all passage of air therethrough. This, in turn, would reduce the pressure drop across the columns and would therefore inhibit air circulation through the grain which is necessary for successful uniform drying.

The means by which the air leaving the dryer is filtered is a screen of woven stainless steel or other nonrusting wire of a mesh fine enough to trap the particles to be removed from the air. The material of the screen and the mesh size may be determined by the municipal authorities in the area where the dryer is to operate. The size of the screen is determined by the area of the dryer, including the base, which is to be covered by the screen. Thus in the illustrative example the dryer is cover-on each side by two adjacent sheets 35 and 36 of screen material of rectangular outline laid in overlapping relation upon the outer edges of the angle iron sides 31 which, it will be remembered, extend transversely of the axis of the dryer; that is, transversely of the plane of the perforated sheet 10. The edges of the screen are folded under for approximately 1 inch from the edge to give a rounded edge to the screen and to reinforce the edge regions thereof. The upper edge of each screen section may be rolled or folded around a rod 37 and the ends of the rod, which extend beyond the ends of the screen, may be secured to the frame of the dryer in the manner shown in FIG. 6, for example. Thus the rod may have an opening drilled therethrough at each end through which passes a bolt 38, the threaded end of which extends through a suitable opening in a bracket 39 secured to said frame. A nut 40 serves to tighten the rod and the screen rolled therearound to the frame of the dryer. Other means for fastening the upper edge of the screen sections to the frame will suggest themselves to those skilled in the art.

The said upper edges of the sections are fastened below the top of the dryer to leave openings 41 through which access to the feed auger may be had. Said openings are covered by an angularly bent sheet 42 which is appropriately hinged along one longitudinal edge (not shown) to the frame so that said sheet may be lowered over the openings or raised from them as shown in FIG. 1 as desired to provide access to the load auger 13.

The intermediate section of each sheet is calculated to overlie the junction between the curved wall and the vertical base wall. Said intermediate section is therefore held pressed against the frame at that junction by a similar rod 43 and brackets such as bracket 39. Due to the difficulty of gaining access to the frame at the junction between the two screens, a single rod extending across both screens may be utilized. This is true of the upper ends of the screens as well. A similar rod 44 and holding brackets may be utilized to hold the bottom edge 45 of the screens against the concrete block structure, when such block structure is used. The ends 46 of the lower portion of the dryer not covered by the imperforate sheet of the plenum chamber are permanently enclosed with the same screen material in any suitable manner.

To avoid fretting of the screen against the edges of the angle irons 31 due to vibration of the dryer, and to provide a flexible seal which will conform to the shape of the screen, commercially available weather stripping material 47, or door seal material may be applied to the transversely extending legs or sides 31 of the outer angle irons 27. Said weather stripping contains a bead 48 of soft resilient material which extends slightly beyond the outer edge of the angle irons so as to be contacted by the screen 35.

The clean-out area below the dryer and within the base defined by struts 32 can be readily reached by simply removing the lower rod 24 on either side of the dryer and raising the lower portion of the screen out of the way.

In the normal operation of the dryer, fan 19 will be operated continuously and burner 18 will be operated intermittently, first during short intervals to maintain a given temperature within plenum chamber 22, and then at longer intervals to provide a cooling cycle for the grain being dried. During the cooling cycle, fan 19 draws ambient outside air into the plenum chamber and forces it through the perforated walls of the columns of grain being dried to the space between the screen and the outer perforated wall. This cooling cycle air is at a temperature of approximately to F so that it will keep the screen at a higher temperature than the outside air. This will eliminate any condensate from forming on the screen during the cooling cycle. It will alsoprevent any condensate from forming on the material removed from the air by the screen and which may momentarily be lodged in the screen.

The length of the sides 31 is somewhere between 1 and 2 inches depending upon the size of the dryer. This spacing of the screen from the outer perforated wall of the dryer is ideal from the standpoint of preventing condensate forming on the screen during either the heating or cooling cycles of the dryer and yet is sufficiently large to permit the particles removed from the air to fall freely through the space into the clean-out area below the dryer. It has been found that the vibration produced by the load and unload augers, by the fan and by the intermittent operation of the burner, is sufficient to dislodge particles tending to adhere to the screen or tending to accumulate on the lower curved section of the screen, and to cause such particles to continue to move downward into the clean-out area. The result is a self-cleaning screen.

Thus, although the dryer may be used continuously for a month or more, it is not necessary to remove, shake out, scrape or otherwise dislodge particles tending to adhere to the screen. It has been found in actual tests on corn that such self-cleaning operation will continue despite rain or snow falling on the screen and despite sudden drops in temperature below freezing. The amount of unwanted particles removed from the air which passed through crevasses between the screen and frame during a l-month operation was negligible whereas during a comparable period and in the same location and under identical conditions, a dryer not provided with the screen of this invention produced piles of particles, and the usual bees wings which accompany corn, around the base of the dryer and in diminishing amount on buildings across the street from the dryer.

Although this invention has been described with reference to a particular type of dryer having an angle iron rib structure frame, it can be used equally effectively with smooth-walled dryers to which may be applied a spacer of the proper width to give the desired spacing between the screen and the wall. It is believed, however, that in order to keep the particles removed from the grain in a dry and hence freely movable state, it is necessary to treat such particles in the same manner as the grain being dried; namely, it should be cooled with fresh outside air to substantially ambient temperature to avoid the condensing of moisture from moist air previously passed through the wet corn or grain on the removed particles.

It is also understood that instead of two screens on each side, a single screen can be used on each side where the dryer is not very long, or more than two sheets can be used on very long dryers.-

I claim:

1. In combination, a dryer for particulate matter, and dryer comprising spaced inner and outer perforated walls forming a column for grain to be dried through which heated air and foreign particles pass to the exterior of the dryer, a screen spaced from the outer perforated walls in the air stream from said perforated outer wall to filter out said foreign particles, means for reducing the temperature of said screen with air having less moisture than the heated air coming from said perforated outer walls, and means for holding said screen in proximity to said perforated walls.

2. The combination defined in claim 1, and means for continuously vibrating said means for holding said screen in proximity to said perforated walls.

3. The combination defined in claim 1, said means for holding said screen in proximity to said perforate wall comprising a frame, means for securing said perforate wall to said frame on one side thereof, and means for securing the screen to the other side of said frame.

4. The combination defined in claim 1, said means for holding said screen in proximity to said perforate wall comprising a plurality of vertically disposed angle iron members, said members having one side parallel to and secured to said perforate walls, said screen bearing against the edges of the other sides of said angle irons and kept in predetermined spaced relation to said perforate walls by said other sides of said angle irons.

5. The combination defined in claim 1 said dryer having a fan for moving a stream of ambient air through said perforated wall, and means for intermittently heating said air, said dryer having double perforate walls containing particulate matter to be dried, said ambient air when not heated by said intermittent heating means acquiring heat from said perforate walls and from the particulate matter contained therebetween, whereby to cool said screen and the foreign particles on said screen while maintaining the moisture content thereof substantially constant.

6. The combination defined in claim 1, said dryer having perforated inner walls in spaced relation to the perforated outer walls to form columnar bins for holding grain to be dried, said inner and outer walls being curved to meet at the top and bottom of the dryer, a substantially vertical base section supporting said perforated inner and outer walls, means for securing the screen to the top of said dryer, said base section extending substantially under the entire length of the dryer, but being narrower than said dryer such that the central portion of the perforated walls extend over the base, and means securing the screen to the top and bottom of the base section.

7. The combination defined in claim 6, said means for holding the screen in proximity to the perforated wall comprising a frame for the dryer having spaced ribs constructed of angle irons, said perforated outer walls being secured to one leg of the angle irons, and

said screen being disposed upon the edge of the other leg of the angle irons.

8. The method of removing foreign particles from a stream of heated air containing large quantities of moisture comprising interposing a screen of appropriate mesh to catch said particles in said stream of heated air, and cooling said screen and particles with air having less moisture than said stream of heated air to a temperature above the dew point of said cooling air.

9. The method as defined in claim 8 comprising the further steps of passing heated air through a column of wet grain to form said stream of heated air containing large quantities of moisture.

10. The method as defined in claim 8 comprising the further step of passing ambient air through a heated column of dried grain and effecting said cooling of said screen with said ambient air after it has passed through said heated column of grain.

11. The method as defined in claim 8 comprising the further steps of alternately passing heated air and ambient air through a column of wet grain to form with said heated air the stream of heated air containing large quantities of moisture and for effecting said cooling of said screen with said ambient air after the heated air is passed through the column of grain.

12. The method as defined in claim 8 comprising the further step of creating a stream of air by a rotatable fan which inherently produces vibrations in the frame thereof, and subjecting the screen to vibrations produced by said fan.

. f- UNITED STATES PATENT OFFICE CERTIFICATE OF CQRRECTION Patent No 3,747,225 Dated July 24, 1973 InT/entofls) Erhard E. Alms It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 19, delete "and" after the word 'Fplenum".

Col. 7, line, 1 3, change 'and" to -said----.,

Signed and sealed this 18th da of December 1973.

(SEAL) Attest;

EDWARD M. FLETCHER, JR. RENE D... TEG'I'MEYER Attesting Officer Acting Commissioner of Patents 

1. In combination, a dryer for particulate matter, and dryer comprising spaced inner and outer perforated walls forming a column for grain to be dried through which heated air and foreign particles pass to the exterior of the dryer, a screen spaced from the outer perforated walls in the air stream from said perforated outer wall to filter out said foreign particles, means for reducing the temperature of said screen with air having less moisture than the heated air coming from said perforated outer walls, and means for holding said screen in proximity to said perforated walls.
 2. The combination defined in claim 1, and means for continuously vibrating said means for holding said screen in proximity to said perforated walls.
 3. The combination defined in claim 1, said means for holding said screen in proximity to said perforate wall comprising a frame, means for securing said perforate wall to said frame on one side thereof, and means for securing the screen to the other side of said frame.
 4. The combination defined in claim 1, said means for holding said screen in proximity to said perforate wall comprising a plurality of vertically disposed angle iron members, said members having one side parallel to and secured to said perforate walls, said screen bearing against the edges of the other sides of said angle irons and kept in predetermined spaced relation to said perforate walls by said other sides of said angle irons.
 5. The combination defined in claim 1 said dryer having a fan for moving a stream of ambient air through said perforated wall, and means for intermittently heating said air, said dryer having double perforate walls containing particulate matter to be dried, said ambient air when not heated by said intermittent heating means acquiring heat from said perforate walls and from the particulate matter contained therebetween, whereby to cool said screen and the foreign particles on said screen while maintaining the moisture content thereof substantially constant.
 6. ThE combination defined in claim 1, said dryer having perforated inner walls in spaced relation to the perforated outer walls to form columnar bins for holding grain to be dried, said inner and outer walls being curved to meet at the top and bottom of the dryer, a substantially vertical base section supporting said perforated inner and outer walls, means for securing the screen to the top of said dryer, said base section extending substantially under the entire length of the dryer, but being narrower than said dryer such that the central portion of the perforated walls extend over the base, and means securing the screen to the top and bottom of the base section.
 7. The combination defined in claim 6, said means for holding the screen in proximity to the perforated wall comprising a frame for the dryer having spaced ribs constructed of angle irons, said perforated outer walls being secured to one leg of the angle irons, and said screen being disposed upon the edge of the other leg of the angle irons.
 8. The method of removing foreign particles from a stream of heated air containing large quantities of moisture comprising interposing a screen of appropriate mesh to catch said particles in said stream of heated air, and cooling said screen and particles with air having less moisture than said stream of heated air to a temperature above the dew point of said cooling air.
 9. The method as defined in claim 8 comprising the further steps of passing heated air through a column of wet grain to form said stream of heated air containing large quantities of moisture.
 10. The method as defined in claim 8 comprising the further step of passing ambient air through a heated column of dried grain and effecting said cooling of said screen with said ambient air after it has passed through said heated column of grain.
 11. The method as defined in claim 8 comprising the further steps of alternately passing heated air and ambient air through a column of wet grain to form with said heated air the stream of heated air containing large quantities of moisture and for effecting said cooling of said screen with said ambient air after the heated air is passed through the column of grain.
 12. The method as defined in claim 8 comprising the further step of creating a stream of air by a rotatable fan which inherently produces vibrations in the frame thereof, and subjecting the screen to vibrations produced by said fan. 